There has been a dramatic increase in the need for bioactive compounds with novel activities. This demand has arisen largely from changes in worldwide demographics coupled with the clear and increasing trend in the number of pathogenic organisms that are resistant to currently available antibiotics as well as the need for new industrial processes for synthesis of compounds. For example, while there has been a surge in demand for antibacterial drugs in emerging nations with young populations, countries with aging populations, such as the U.S., require a growing repertoire of drugs against cancer, diabetes, arthritis and other debilitating conditions. The death rate from infectious diseases has increased 58% between 1980 and 1992 and it has been estimated that the emergence of antibiotic resistant microbes has added in excess of $30 billion annually to the cost of health care in the U.S. alone. (Adams et al., Chemical and Engineering News, 1995; Amann et al., Microbiological Reviews, 59, 1995). As a response to this trend pharmaceutical companies have significantly increased their screening of microbial diversity for compounds with unique activities or specificities.
The majority of bioactive compounds currently in use are derived from soil microorganisms. Many microbes inhabiting soils and other complex ecological communities produce a variety of compounds that increase their ability to survive and proliferate. These compounds are generally thought to be nonessential for growth of the organism and are synthesized with the aid of genes involved in intermediary metabolism. Such secondary metabolites that influence the growth or survival of other organisms are known as ≅bioactive? compounds and serve as key components of the chemical defense arsenal of both micro- and macroorganisms. Humans have exploited these compounds for use as antibiotics, antiinfectives and other bioactive compounds with activity against a broad range of prokaryotic and eukaryotic pathogens (Barnes et al., Proc. Nat. Acad. Sci. U.S.A., 91, 1994).
The approach currently used to screen microbes for new bioactive compounds has been largely unchanged since the inception of the field. New isolates of bacteria, particularly gram positive strains from soil environments, are collected and their metabolites tested for pharmacological activity.
There is still tremendous biodiversity that remains untapped as the source of lead compounds. However, the currently available methods for screening and producing lead compounds cannot be applied efficiently to these under-explored resources. For instance, it is estimated that at least 99% of marine bacteria species do not survive on laboratory media, and commercially available fermentation equipment is not optimal for use in the conditions under which these species will grow, hence these organisms are difficult or impossible to culture for screening or re-supply. Recollection, growth, strain improvement, media improvement and scale-up production of the drug-producing organisms often pose problems for synthesis and development of lead compounds. Furthermore, the need for the interaction of specific organisms to synthesize some compounds makes their use in discovery extremely difficult. New methods to harness the genetic resources and chemical diversity of these untapped sources of compounds for use in drug discovery are very valuable.
A central core of modem biology is that genetic information resides in a nucleic acid genome, and that the information embodied in such a genome (i.e., the genotype) directs cell function. This occurs through the expression of various genes in the genome of an organism and regulation of the expression of such genes. The expression of genes in a cell or organism defines the cell or organism's physical characteristics (i.e., its phenotype). This is accomplished through the translation of genes into proteins. Determining the biological activity of a protein obtained from an environmental sample can provide valuable information about the role of proteins in the environments. In addition, such information can help in the development of biologics, diagnostics, therapeutics, and compositions for industrial applications.
Accordingly, the present invention provides methods to access this untapped biodiversity and to rapidly screen for sequences and activities of interest utilizing recombinant DNA technology. This invention combines the benefits associated with the ability to rapidly screen natural compounds with the flexibility and reproducibility afforded with working with the genetic material of organisms.